1. Field of the Invention
The present invention relates to implantable inflatable devices, and in particular, it relates to an implantable skin expansion device.
2. Description of the Prior Art
Present tissue expansion technology includes the implantation of a device having an inflatable envelope beneath the skin. One example of such an inflatable device is described in the Radovan et al U.S. Pat. No. 4,217,889, which is presently assigned, in part, to the same assignee as the present invention. The device of the Radovan et al patent is incrementally expanded over a period of time to develop additional tissue surface that is used for surgical reconstruction or repair.
The following patents describe other types of skin expanders and inflatable protheses:
______________________________________ Inventor U.S. Pat. No. ______________________________________ Pangman 2,842,775 Boone 3,600,718 Arion 3,860,969 Lynch 3,883,902 Lake 4,095,295 Cox, Jr. 4,178,643 Schulte 4,190,040 Lincoff 4,299,227 Berguer 4,309,776 Sahbabian 4,312,353 Bartolo 4,428,364 Hyans 4,459,318 ______________________________________
The Radovan et al. device includes an inflatable envelope attached to a base. A filling tube is glued or flanged to the inflatable envelope at one end and is connected to an injection chamber at another end which is implanted a distance away from the envelope. There are several disadvantages associated with attaching the filling tube to the inflatable envelope.
When the inflatable envelope is inflated, it rises. The area where the tubing is connected to the inflatable envelope or junction also rises. The rising junction results at times in local necrosis of surrounding tissue and erosion of the device. Also, during inflation, the rising junction of the tubing and the inflatable envelope results in the junction being moved further from the injection chamber since the injection chamber is stationarily implanted, and results in increased tensile forces on the envelope proximate the junction. The increased tensile load remains until the device is deflated.
In addition to the increased tensile load, stresses occur proximate the junction from constant flexing while the device is implanted since the filling tube and the envelope have different flexural moduli. The stresses due to the constant flexing at the junction result at times in a compromise of the envelope integrity.
After the envelope is deflated, the envelope is removed through a relatively small incision. The envelope is often simply pulled through the incision by pulling on the filling tube. The tubing and envelope may separate during removal resulting in an inconvenience to the surgeon.